The present disclosure relates to a method for transmitting data between a control device and at least one measurement device by means of a bus system, wherein the measurement data resolution and the measurement frequency of the measurement device can be dynamically adjusted, and also to a battery management unit.
It is becoming apparent that battery systems or batteries on which very strict requirements in respect of reliability are made will increasingly be used in the future, both in stationary applications and also in vehicles such as hybrid and electric vehicles. The reason for said strict requirements is that failure of the battery can lead to a safety-critical problem.
In order to be able to guarantee the reliability of a battery system, the battery cells and battery modules of said battery system are monitored by electronic measurement and control devices. Nowadays, electronic measurement devices and/or control devices are increasingly being used in the automobile sector in particular. Examples of said electronic measurement devices and control devices are the engine control device, ABS control devices or the control device for the airbag of a vehicle. The development of batteries and/or battery systems with an associated battery management system which comprises measurement and control devices with software for monitoring the battery functionality is also required for electrically driven vehicles. Batteries of this kind have a wide variety of topologies, based on the number and arrangement of the battery cells and/or battery modules and sensors or measuring devices of said batteries, depending on the customer requirements or the installation space available.
Typical battery management systems monitor and control the currents, the voltages, the temperatures, the insulation resistance and other variables of the battery cells and battery modules. Management functions which increase the service life, reliability and safety of the battery system can then be executed with the inclusion of these variables. The majority of battery management systems known from the prior art have a control device topology with a central control device (also called main control device) and a plurality of subordinate sensor control devices. In order to detect measurement data relating to the various measurement variables of the battery cells, the sensor control devices are connected to measurement devices or are contained in said measurement devices, that is to say they are, for example, built into the measurement devices. In this case, measurement variables can be, as mentioned, for example, voltages, temperatures or currents of the battery cells and/or battery modules which are measured and/or detected directly at said battery cells and/or battery modules. The detected measurement data is transmitted from the measurement devices, by means of a bus system (for example by means of a CAN bus), to the central control device or to the main control device. To this end, the measurement data which is recorded by the measurement devices and which has a specific measurement data resolution is transmitted to the bus system at a predetermined measurement frequency.
The total amount of measurement data which can be transported on the communication bus over a specific time is limited by the use of a bus system with a defined bandwidth. As a result, the transmission of measurement data from the measurement devices to the central control device is restricted. For example, a greater quantity of data has to be transported in the case of a high level of measurement accuracy, that is to say at a high measurement data resolution, than at a lower measurement data resolution. Furthermore, the additional communication by other bus subscribers by means of the bus system further restricts the available bandwidth of the bus system. This additional communication may be, for example, diagnosis or control commands which the central control device transmits to the sensor control devices and/or measurement devices by means of the bus system.
As a result, the maximum measurement frequency is also determined when selecting a measurement data resolution during the design of the software. In this case, it is no longer possible to pass or transmit all the measurement data to the bus system at a relatively high measurement frequency.